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THz Spectroscopy Method for Substance Detection and Its Identification

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (20 December 2021) | Viewed by 8369

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Special Issue Editor

Prof. Vyacheslav A. Trofimov

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Guest Editor

School of Mechanical & Automotive Engineering, South China University of Technology, Guangzhou 510640, Guangdong, China
Interests: interaction of laser beam and pulse with semiconductor; photonic crystal; nanoparticles; propagation of femtosecond terawatt laser pulse; optical bistability and multistability; chirped and aberrated optical solitons; frequency conversion of femtosecond pulse; four waves mixing; detection and identification of substances using THz pulsed spectroscopy; passive THz imaging; IR imaging; computer simulation; mathematical modeling; conservative finite-difference scheme; invariants of nonlinear laser pulse and beam interaction with substance

Special Issue Information

Dear Colleagues,

It is a great pleasure, and an honor, to present this Special Issue of Applied Sciences.

The THz band of frequencies is attracting increased interest from the military, security, and medical fields mainly due to the THz signatures. The spectral signatures of threats have become well known to exploit them for security screening purposes. Using machine recognition techniques increases the threat recognition rate. There are some demonstrations of succeful applications of THz TDS for food quality control as well as oil quality control. Futher developing THz TDS methods allows enhancing the efficiency of the detection and identification of the substance and extending of THz spectroscopy application field.

You are cordially invited to submit your original research or review papers to this Special Issue. All papers need to present original, previously-unpublished work and will be subject to the normal standards and peer-review processes of this journal.

Prof. Vyacheslav A. Trofimov
Guest Editor

Manuscript Submission Information

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Keywords

Broadband THz pulse
detection and identification substance
reflection and transmission mode
Surface
Bulk material
Powder material
Pulsed THz spectroscopy
Noisy THz signal
Spectral Resolution enhancement
Food quality
THz device
Computer simulation
Maxwell’s equations
Methods of THz generation and registration
Security screening
Nondestructive testing for industry
Postal mail and package screening

Published Papers (5 papers)

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Research

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21 pages, 868 KiB

Open AccessArticle

Frequency Down-Conversion of Optical Pulse to the Far Infrared and THz Frequency Ranges Due to the Cascading Process in a Medium with a Quadratic Nonlinear Response

by Vyacheslav A. Trofimov, Dmitry M. Kharitonov, Mikhail V. Fedotov and Yongqiang Yang

Appl. Sci. 2022, 12(8), 3891; https://0-doi-org.brum.beds.ac.uk/10.3390/app12083891 - 12 Apr 2022

Cited by 1 | Viewed by 1258

Abstract

Difference-frequency generation is a well-known method of obtaining IR and THz radiation. It has many practical applications, such as sensing, optical metrology, diagnostics, detection and identification of substances, etc. One of the generation methods is based on the three-wave interaction in a medium with second-order nonlinear susceptibility. In this study, we investigated a special case of the frequency down-conversion into IR and THz ranges of the frequencies: the frequencies of interacting waves were multiple. We analyzed theoretically two cases of three-wave interactions: amplification of the infrared (or THz) radiation (incident weak intensity of a wave at this frequency) and a wave generation with the difference-frequency (incident zero-value intensity at this frequency). The amplification efficiency could achieve 75% and the maximal frequency conversion efficiency is about 25%. The computer simulation results made for the femtosecond pulse interaction in a crystal with the wavelength 4, 10, and 24 μm demonstrates applicability of such a scheme for the frequency down-conversion. This scheme of the THz radiation generation is a perspective tool for its application in the screening system for the detection and identification of substances. Full article

(This article belongs to the Special Issue THz Spectroscopy Method for Substance Detection and Its Identification)

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25 pages, 3164 KiB

Open AccessArticle

Ultrafast Time-of-Flight Method of Gasoline Contamination Detection Down to ppm Levels by Means of Terahertz Time-Domain Spectroscopy

by Kamil Stelmaszczyk, Ewelina Karpierz-Marczewska, Valeri Mikhnev, Grzegorz Cywinski, Thomas Skotnicki and Wojciech Knap

Appl. Sci. 2022, 12(3), 1629; https://0-doi-org.brum.beds.ac.uk/10.3390/app12031629 - 04 Feb 2022

Cited by 2 | Viewed by 1896 | Correction

Abstract

In this article, we present the possibility of using terahertz time-domain spectroscopy to detect trace, ppm-level (%wt.) concentrations of admixtures in 95-octane lead-free gasoline in straightforward time-of-flight (pulse-delay) measurements performed directly in the liquid. The method was tested on samples containing 75–0.0125% of isopropanol and 0.3–0.0250% of water. The detection limits for isopropanol and water content were determined to be 125 ppm and 250 ppm, respectively, approaching the limits of much more complicated and time-consuming methods (like spectroscopy of the vapor phase). The measured pulse delays were compared with theoretical calculations using the modified Gladstone-Dale mixing rule for the solutions. The comparison demonstrated good agreement for gasoline-alcohol mixtures and large discrepancies for gasoline-water mixtures, suggesting that gasoline-water mixtures cannot be considered idealized binary mixtures. Our results clearly show that the pulse time delay measurement by THz-TDS is a fast and sensitive method of gasoline contamination detection and, as such, can be easily integrated with industrial online real-time quality control applications. Full article

(This article belongs to the Special Issue THz Spectroscopy Method for Substance Detection and Its Identification)

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10 pages, 828 KiB

Open AccessCommunication

Superposition of 2ω and Electrostatic Field Induced Terahertz Waveforms in DC-Biased Two-Color Filament

by Aleksandr Ushakov, Pavel Chizhov, Irina Nikolaeva, Daniil Shipilo, Nikolay Panov, Vladimir Bukin, Kseniia Mamaeva, Olga Kosareva and Sergey Garnov

Appl. Sci. 2021, 11(24), 11888; https://0-doi-org.brum.beds.ac.uk/10.3390/app112411888 - 14 Dec 2021

Cited by 5 | Viewed by 1793

Abstract

Increase in conversion efficiency from a femtosecond optical pump into broadband terahertz (THz) radiation is currently an essential issue since it boosts THz source performance for medicine and security applications. An air-plasma based THz radiation from a two-color femtosecond filament is the most efficient gas-based THz emitter, with a dipole local source having a maximum on the beam propagation axis. In this work, we show the novel advancement to THz yield increase with preservation of the forwardly directed dipole radiation. The two-color THz source can be enhanced if the filament plasma channel is placed into an external electrostatic field (DC bias), which is parallel to the second harmonic polarization direction. In the experiment, we produce a plasma channel from 800-nm, ∼50-fs, 2-mJ pulse with 200

μ

J of 400-nm, ∼50-fs mixed with the pump, and allocate it between the electrodes carrying 7-kV/cm static field. Time-domain measurements and

3 D

+time simulations of THz waveforms from the two-color DC-biased filament show that the THz emission is the superposition of the THz waveforms generated in the

800 + 400

-nm filament without a DC-bias and in the 800-nm (without 400-nm) plasma channel biased by 7-kV/cm static field. The additivity of the two local dipole THz sources is possible if the majority of free electrons are produced by the pump pulse. Full article

(This article belongs to the Special Issue THz Spectroscopy Method for Substance Detection and Its Identification)

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10 pages, 2483 KiB

Open AccessArticle

Analysis of the Thermal Decomposition Products of Pathological and Healthy Tissues in Paranasal Sinuses: A High-Resolution Terahertz Gas Spectroscopy Study

by Vladimir Vaks, Andrey Aizenshtadt, Vladimir Anfertev, Maria Chernyaeva, Elena Domracheva, Kseniya Gavrilova, Roman Larin, Sergey Pripolzin and Mariya Shakhova

Appl. Sci. 2021, 11(16), 7562; https://0-doi-org.brum.beds.ac.uk/10.3390/app11167562 - 18 Aug 2021

Cited by 6 | Viewed by 1513

Abstract

We present the novel results of studying tissue metabolites of the ear-nose-throat organs (pathological and relatively healthy mucosal tissues) during heating and thermal exposure using gas spectrometers of the terahertz (THz) frequency range based on non-stationary effects. Tissue metabolites of the ear-nose-throat organs obtained during surgery according to strict medical indications have been studied for the first time in the world. All the tissues used in the samples were histological verified for confirming the morphological diagnosis. For obtaining a unified picture, chemical compounds appearing during thermal decomposition of pathological and relatively healthy tissues were identified using the spectroscopic approach, with mandatory histological verification of the samples. The obtained results demonstrate that a powerful research tool has been proposed for evaluation of metabolites in otorhinolaryngology with detection of diseases markers. Full article

(This article belongs to the Special Issue THz Spectroscopy Method for Substance Detection and Its Identification)

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